Leonard Thomas Dunmore, 21, accused of carrying pipe bombs into an office at Landover Mall Wednesday and holding 12 women hostage, was sent to a Maryland state hospital for psychiatric observation yesterday after he told a Prince George's County judge that he had been treated in the past for "paranoia."

"Some of it was not induced by myself, so I don't blame it all on myself," said Dunmore, his arms wrapped in chains and his wrists handcuffed as he stood before District Court Judge Bond L. Holford.

Earlier in the hearing, held to set bond, Dunmore's public defender, James S. Nickelsporn, told the court that Dunmore had twice been treated at St. Elizabeths Hospital for the mentally ill in Washington. Police have said he was sent to the hospital after he threatened President Reagan.

Nickelsporn and a police psychologist said Dunmore had been diagnosed as suffering from paranoid schizophrenia. That disorder is commonly described by experts as severe detachment from reality, often characterized by depression and feelings of persecution.

Holford ordered that Dunmore, who lives with his parents in a quiet, residential neighborhood in Glenarden, immediately be taken to the Clifton T. Perkins Hospital, the state's maximum security psychiatric hospital, to determine if he is competent to stand trial on the charges against him. No bond was set.

There were no injuries during the takeover Wednesday, which began at about 2 p.m. when police received a call from a woman at an office of the state Vocational Rehabilitation Center, located at the mall. The caller told police that she and others there were being held hostage by a man who said he had a bomb in his briefcase. The women were held for 2 1/2 hours until police helped them escape through a hole that was cut in a plasterboard wall leading to a clothing store.

Dunmore, who was dressed in camouflage clothing and had demanded, among other things, some iced tea, cigarettes and an assortment of rock music, surrendered peacefully three hours later. He was charged with one count of kidnaping, manufacturing and possession of explosives.

"We are not certain that he understands all of the ramifications," public defender Nickelsporn said during the hearing about the charges against Dunmore. Nickelsporn said that Dunmore had been "rambling" at times, that he was not always aware of where he was and that "he is not able to rationally communicate with us at this time." Assistant State's Attorney Edmund O'Connell agreed with Nickelsporn that Dunmore should undergo psychiatric examination. A report is to be submitted to the court within 30 days.

Surrounded by sheriff's deputies, Dunmore muttered unintelligibly during parts of the hearing and at one point, just after he was brought into court, he said out loud, "The kidnaping of those people down in Texas was insignificant." Dunmore said nothing further related to that statement.

According to Prince George's County police, the women who were taken as hostages said in later interviews that they did not believe Dunmore had been a client at the vocational rehabilitation office.

Dunmore's father, Benjamin Dunmore, an engineer at the Harry L. Diamond government research laboratories in White Oak, said in a telephone interview yesterday that his son was unemployed and that he was "highly interested" in mathematics and science.

Leonard Dunmore, who lives at 7806 Glenarden Parkway and is called "Lennie" by his friends, received a diploma in 1981 from Eleanor Roosevelt High School in Greenbelt through the county schools' home teaching program.

In the fall of 1981, Dunmore was enrolled in Prince George's Community College, where he took courses in composition and college algebra and according to knowledgeable sources, attained a 4.0 grade point average.

Dunmore's boyhood friends, interviewed in the Glenarden neighborhood yesterday, said that Dunmore spent much of his time inside the family's one-story home.

"He really wouldn't go anywhere except if I took him," said Mark Sowell, 23, who said he has known Dunmore since childhood. Sowell and other friends and neighbors interviewed yesterday said they firmly doubted that Dunmore would ever intend to harm anyone and that they were convinced that Dunmore's alleged action yesterday was a plea for attention.

Kenneth Miller, 22, and Anthony Holbert, 21, who described themselves as Dunmore's "closest friends, the ones who care," said yesterday that Dunmore had been a generous companion to them, giving them food and cigarettes and even money when they needed it, sometimes cooking for them, and once even taking a hot omelet to Holbert while he was at work.